Aqueous emulsion paint



Patentedluly 23,1946

"PATENTflames I if nouaousmgonrnm'r v Q iv f Marvin '1. Schmidt, Chicago, 111., assignor to United States Gypsum Company, Chicago," 111.,

a corporation of Illinois No Drawing.

' This invention relates to an improvement in the I Application February 23, 1944, Serial No. 523,581

' ill-Claims. (01. 106-143);

- hence cannot be properly-sized art of manufacturing colored washable emulsion paints sometimes referred to as resin emulsion paints and more particularly to a paint which is uniform in color and free from streaking and blotching when applied to ordinary surfaces. i It is the purpose of this invention to produce a colored emulsion .paint which is substantially freefrom blotching andstreaking when applied in thin film form, particularly to surfaces which are high inabsorption such as plasterboard or a lime putty finish. v

It is well known that colored emulsion paints, such asthose madev using alkyd resins, as well as other 'film forming materials, will sometimes show differences in color when applied over surfaces exhibiting different degrees of fsuction" in various areas, though the paintitself is uniform; and in addition, these paints often show differences 1 of color as streaks along the path of the brush when the paint is appliedover such surfaces. When a painted surface exhibits either brush streaks or.

blotches a very undesirable condition exists which is a consistent cause for complaint in the field. Unfortunately, colored surface does not always result in an improvement of the surface, but in many cases magnifies the difficulty. The exact cause of these conditions is not known but itis believed due to irregular absorption of the surface.

-'In the description of this invention the term blotching is defined-to mean-the variation in shade in localized areas different'from the field color when the same shade of paint is used throughout, and where such diflerence is not accountable for by a corresponding difference in repainting the non-uniform until- One of the outstanding :advanta'ges 'of an aqueous emulsion'paint is that it can'be applied-to green walls without previous drying, and to; dry} and size the wall so that it can be painted would be doing away with one of the big advantages in using this type'ofpaintr I I It has been discovered that by the simple addi-' tion of certain materials this difiiculty of streaking and blotching can be practically completely eliminated. Thus if difilculty' of this type is encountered in actual field application, it'can be overcome merely by mixing a small quantity of the inhibitingmaterlal into the paint.

The materials that accomplish the purpose of this invention were obtained as a result of a great color of the surfacebeing painted. Also, by the term streaking ,is meant the color variation which followsthe path of the brush strokes in parallel lines like the ridges and depressions following the brush though there-may not be such ridges and depressions.

difflculty, of streaking and blotching can be overcomeby first thoroughly sealing or priming the surface with a vamishtype of surfacing material. This treatment is expensive when ap-' plied only for this purpose as in general it is not ordinarily neededto accomplish any other purpose. In fact, many of the walls to which an emulsion paint is to be applied are "green and number of trials using various types of materials. No predictions arising out'of knowledge commonly known to those skilled in the art could be made. No explanations can be made as to why only certain few materials will work satisfactorily while a great range of other materials will not. Numerous theories were considered, but no data to'support them could be evolved.

Only a very limited number of materials can ;be used for the purpose, One classof materials which has beenv found satisfactory is the fatty acid esters of polyethyleneglycols, such as the type known as and sold under the trade name of Carbowax 4000 and manufactured by the Carbide and CarbonCompany. It has been found thatthe, esters of saturated or unsaturated fatty acids of between 12-24, inclusive, carbon atoms, particularly stearic, :formed with a polyethylene glycol'such as CarbowaxAOOO, asreferred to above, are very well suited for carrying out this invention.- streaking and blotching form' the subject'of another application, Serial No. 523,580, filed February 23, 1944. 1

In carrying out this invention, it is preferred to the polyethylene glycol ester to the paint in'the field. For purpose of illustrating the preferred methodof carrying out this invention in the fol-' lowing example, the material will be added during formulation. 1

Other materials which prevent The forthcoming example clearly describes a paint composition which but for the inhibiting material incorporated therewith will result in pronounced streaking and blotching when applied to many types of surfaces.

The ester gum-linseed oil binder is prepared by heating to a temperature of 580 degrees F. for about one hour, 41.5 lbs. of ester gum. with 124.5 lbs. of heat bodied linseed oil. The cobalt drier is then added. The drier can be of the naphthenate type. This mixture, while in liquid form, is emulsified, by any of the well known methods of preparing an emulsion. with the casein solution to form a binder. Most any type of casein solution can be used. A suitable casein solution is one which is described in U. S. Patent No. 2,154,362. This can be used to advantage as it is stable for a. considerable length of time to (18561710! ration due to aging. However, the preparation of casein or other protein solutions using alkalies such as borax for use in emulsion paints is well established in the art and a detailed description of a procedure for making them need not be included in the description of this invention.

' For the sake of convenience for those who may not be familiar with this art and with U. S. Pate ent No. 2,154,362, the following procedure, which is based upon the above patent can be used in preparing a casein solution. Following this patent the casein solution can be prepared by mixing 55 lbs. of commercial casein with 24 gallonsof water with thorough stirring for a suflicient length of time until a smooth mixture of thoroughly soaked casein results. About 3 pounds and 6 /2 ounces of sodium stannate are dissolved;

in about 3 /2 gallons of water, while in a. separate container about 10 lbs, of borax are likewise dissolved in about 2 /2 gallons of hot water. The

sodium stannate solution is then added to'the casein mixture, with constant agitation, and as soon as all of it has been added, the borax solution is then run into the mixture. An additional a 60 added and the mixing continued while heating 5 the mixture gradually to about 150 to 160 degrees amount of, say, 3 gallons of water may then be F. or higher. The mixing. is continued at the desired temperature until a smooth solution results. Using the proportion above given, the solution will be found to exhibit an alkaline reaction equivalent to from about pH 8.0 to pH 9.0. The

ratio of casein to sodium stannate in the above formula "is substantially 10026.2. The sodium stannate used has the following formula: Na2SnOa.3H2O. While casein is' the preferred type of protein, other proteins may be used ineluding those derived from vegetable sources, for example alpha protein derived from soya beans. When the emulsion has been prepared, using Emulsion .Pounds Ester gum-linseed oil binder 166 6% cobalt drier 1 8 Casein solution, so1idsj 340 Paste paint 1 Emulsion- 514.0 Phthalocyanine blue 31.6 Cadmium yellow 31.6 Bone black 4.75 Titanium dioxide 900 Fine mica 60 Pine oil Water approx 350 Carbowax ester 25% solids 35-280 4 additional water if necessary, the dry pigments and other ingredients are added and mixed in a suitable type of mixer. is preferably added last.

The Carbowax stearate can be made by reacting polyethylene glycol. i. e., Carbowax 4000, with stearic acid or it can be purchased already prepared from the Carbide and Carbon Chemicals 0011)., as well as other sources. It is preferred to add this material as a waterpaste, and containing about 25% of the solid material. This is prepared by heating 25'parts of the Carbowax stearate in 75 parts of water. Various modifications of the Carbowax, such as Carbowax 1500, can be used as well as equivalent materials sold under different trade names. Any of the polyethylene glycols can be used as long as the properties are such as to accomplish substantially the same results as with Carbowax 4000. It is not intended to limit this application to the addition of the stearatein paste form to the paint already prepared for it may be added in any manner and at any time during the formulation or use of the paint as long as the effective result of this material is obtained.

Neither is it the intention to limit the scope of this invention to a neutral ester of a fatty acid;

for the polyethylene glycol need not all be ester-, ified, though a mere solution of the glycol in the fatty type of acid is not enough. The mixture must be heated to effect some type of reaction;

between the two which need not 'be an entirely pure ester in itself. There can be an excess of the acid over that of the polyethylene glycol and excellent results will. still be obtained. Hence. throughout the specifications and claims of this invention the word ester" is intended to mean a mixture of a fatty acid and a polyethylene glycol polyethylene glycol in same manner. 'In other words, an ester interchange can be used to prepare the polyethylene glycol ester if desired as well as other methods.

After the Carbowax stearate paste has been added and the mixing operation has been completed, the paste is then passed through a roller mill to insure complete dispersion of the pigments into the vehicle and to form a paint completely free from lumps.

Various types of pigments, fillers and other finely divided inorganic material can be used in the preparation of paints which can be benefited by this invention. However, it is necessary that some coloring material be present as streaking and blotching have not been observed to any great extent in white paints. Since water is the thinher, it is possible to use a wide variety of low index of refraction materials such as clays, mica, etc., known in the trade as filler or extenders to replace a certain amount of the more expensive higher index of refraction materials known as pigments, such as lithopone and titanium dioxide, as required in an oil type of paint. Since both types of material can be used, in order to define these two types of material generically, the

word pigment-fillers will be used in the forthcoming claims.

Paint prepared in the above manner will not exhibit the streaking and blotching effects com- The Carbowax stearate I tactics f5, g 16 This is done: without any sacrifice in the desirable'properties'ofthistype of and with onlyaslightincreaseincost.

If the painthas alreadybeenprepared and it isdesired to prevent streaking and blotching, then about 4 to 32 ounces of the 25%,Qarbowax stearate ester paste, mentioned. above, be

added per gallon.- Other esters, of polyethylene glycol canbe Also it is not necessary that the ester be added'in pas'teiorm. It may be expedient in manycases notto add the inhibiting material until actual trouble is experienced as the difficulty is only occasionally encountered.

Examples of the saturated and unsaturated nishes. natural water insolubl'e film forming materials;- theseare pr fe a l by the use 'casein or Although there been disclosed a practical embodiment of this invention and specific exampies and uses, which are .given to, insurea clear understanding ofthe essence of this invention, it is not the intention tobe limited thereby. for obviously many variations m y be made by those skilled inthe art and still be within thescope of this invention which is only limited in extent by the forthcoming claims.

fatty acids besides stearic between 12 andr24 carbon atoms inclusive which can be used in some cases it may be desirable to add an excess of the acid.

In the above example a mixture of ester gum and heat bodied linseed oil is used. It is not the intention to limit this invention to any of the ingredients used in the preferred embodiment set forth, for any water resistant film forming substance which will have utility in a colored emulsion paint may be used. It is not necessary that r the material be a resin, though most of the emulsion paints in common use contain a resinous or polymerizable material, usually oleoresinous. Examples of some of the materials which can be incorporated are: treated or untreated oils having drying properties, alkyd resin, phenol formaldehyde resins, the various esters of rosin, synthetic and natural resins, such as congo gum,

copal gum and manila gum. These can be used alone, in combination or with solvents; the particular manner in which they are used as well as the addition of other materials such as driers and the like are all within the skill of the art of which this'invention is a part and need not be further described.

While it is preferred to use casein or some otherprotein material, such as Alpha protein derived from soya beans, as the emulsifying agent, it is not the intention to limit this invention thereby, for other emulsifying agents which are compatible can be employed. The volatile alkali soaps are especially suitable for the purpose.

It will be found that paints prepared in accordance with the principle set forth in this im vention can be applied over practically any surface without danger of forming an appreciable amount of streaks or blotches. A uniform coloration will be obtained. Water paints applied over a lime putty finish and over wallboard are particularly liable to give trouble, yet no difficulty will be encountered if the paint'is prepared following the principles set forth in this invention.

By way of summary this invention pertains to the prevention of color blotching or streaking in a colored aqueous emulsion paint by incorporating therein a polyethylene glycol ester of fatty acids from 12 to 24, inclusive, carbon atoms. The non-aqueous vehicle may consist of oils, var- It is claimed:

1. A non-streaking, non-blotching, emulsion paint comprising a protein selected from the group consistingof casein and an alkali dispersible vegetable protein derived from soybean, a solvent for said protein, water, a water insoluble film forming material, colored pigment, and a streaking and blotching inhibiting material comprising an ester formed from the reaction of a polyethylene glycol and a fatty acid of from 12 to 24 carbon atoms per molecule.

2. A non-streaking, non-blotching, aqueous emulsion paint comprising a protein selected from the group consisting of casein and an alkali dispersible vegetable protein derived from soybean, a solvent for said protein, water, a

water insoluble film forming material, pigmentiillers, at least one of which is colored, and a streaking and blotching inhibiting material comprising an ester formed from' the reaction of a polyethylene glycol and saturated and unsaturated fatty acids of from 12 to 24 carbon atoms per molecule.

3. The composition of claim 1 in which said water insoluble film forming material is capable of drying by oxidation and polymerization.

4. The composition of claim 1 in which said water insoluble film forming material is a resinous material selected from the group consisting of synthetic resins and natural resins, and a solvent for said resin.

5. The composition of claim 1 in which said water insoluble film forming material is an ester of resin acids.

6. An aqueous resin emulsion paint substantially free from streaking and blotching, comprising a water insoluble film forming material, colored pigment, an emulsifying agent, water, and a streaking and blotching inhibiting material comprising an ester formed from the reaction of a polyethylene glycol and saturated and unsaturated fatty acids of from 12 to 24 inclusive carbon atoms per molecule.

'7. A non-streaking, non-blotching, colored, aqueous emulsion paint comprising a protein selected from the group consisting of casein and an alkali dispersible vegetable protein derived from soybean, a solvent for said protein, water, a water insoluble film forming material, pigmentfillers, at least one of which is colored, and an ester formed from the reaction of stearic acid and a polyethylene glycol.

8. A non-streaking, non-blotching, aqueous emulsion paint comprising a protein selected from the group consisting of casein and an alkali dispersible vegetable protein derived from soybean, a solvent for said protein, water, pigmentfillers, at least one of which is colored, a water insoluble film forming material and from about 1 to about 8 ounces of an ester, formed from the reacper molecule, to each gallon of said aqueous emulsion paint. 1

9. A non-streaking, non-blotching, aqueous emulsion paint comprising casein, a solvent for said casein, a water insoluble fllm' forming oleoresinous material containing an alkyd'resin, pigment-fillers, at least one of which is colored, and

an ester formed by the reaction of polyethylene glycol and a fatty acid selected from the group consisting of stearic, palmitic and oleic acids.

10. An aqueous emulsion paint substantially free from streaking and blotching comprising a water insoluble film forming oleoresinous binder comprising the resulting product formed by heating an oil capable of drying by oxidation and "polymerization with a resin selected from the group consisting of synthetic resins and natural resins,'a volatile alkalisoap emulsifying agent,

water, pigment-fillers, at least one of which is colored, and the ester formed'by heating a mix- '0 ture of polyethylene glycol and a saturated and unsaturated fatty acid containing from 1 2 to 24 inclusive carbon atoms per molecule. I

11. An aqueous emulsion paint substantial] free from streaking and blotching comprising a protein selected from the group consisting oi casein and an alkali dispersibleyegetable protein derivedi'rom soya beans. a solvent for said molecule.

- MARVIN T. SCHMIDT. 

